Cell for electrolysis of melts having a plurality of movable cathodes



Nov. l0, 1964 E. MEIER ETAL 3,156,538

crau. FOR ELEcTRoLYsIs oF MELTs HAVING A PLURALITY oF MovABLE cATHoDEs Filed July 7, 1961 Erich Schweizer ATTORNEYS United States Patent O 3 Claims. (ill. 264-226) The present invention relates to a cell for the electrolysis of melts.

In the electrolytic production of certain metals, particularly high melting metals, by the electrolysis of a melt it is necessary to prevent the deposited metal from coming into contact with the atmosphere when it is discharged from the cell, because at high temperatures these metals readily absorb gases, particularly oxygen, from the atmosphere. However, it is easier to detach the deposited metal from the cathode the higher the temperature, which is advantageously maintained above the melting temperature of the melt residues still adhering to the deposited metal.

The present invention provides a cell for the electrolysis of melts which is provided with means for withdrawing a cathode from the cell and removing deposited metal from the cathode without exposure to the atmosphere, which means comprises a lifting device for retractinga cathode from the cell, at least one enclosure to receive a retracted cathode, such enclosure having means for cooling the cathode therein and a gas-tight seal to permit of retracting an upper part of the cathode out of the enclosure, a stripping device outside the cell for removing deposited metal from the cathode, a receiver for the metal removed from the cathode, and a chamber for protective gas which communicates with the top of the cell and with the said cathode enclosure and within which l the stripping device and the receiver are situated.

Preferably, at least two pivotally mounted cathode enclosures are provided each of which is movable from an operative position occupied when a cathode is in operation within the cell to an inoperative position permitting a used cathode to be exchanged for a fresh cathode.

An apparatus constructed in accordance with the invention is shown by way of example in the accompanying drawings, which shows the apparatus diagrammatically in cross-section.

The cell itself has a pot-shaped anode which consists, for example, of graphite. The anode is contained within a casing 12 which serves for heat insulation and within which is an electric heater coil 14 for heating the melt. Centrally arranged within the cell is a rod-shaped cathode 16 which usually consists of an inert material, for example, nickel or graphite. Between the anode lil and the cathode 16 there is a cylindrical diaphragm 18 which serves to prevent the halogen, for example, chlorine, liberated at the anode from reaching the deposited metal, when halide melts are used.

The upper end 2li of the cathode, which also serves as a supply lead, is rod-shaped and, according to the invention, is guided in a stuiiing box A cathode enclosure trap 22 is constructed as a cooling jacket for the cathode when it is retracted from the cell, a cooling agent flowing between the walls of the jacket. The upper end of the cathode is connected to a lifting device 26, preferably through a releasable coupling 24. The lifting device is constructed as a hydraulic cylinder, as shown in the drawing, which for reasons of space, has not been drawn in its full length. The cylinder is connected to the cell by means of a support 27. Instead of a hydraulic lifting device, other devices, such as a mechanical device, for example, a spindle or toothed rack, may of course be employed. There is also provided for the cathode a stripping device which is shown as a cylindrical edge 28. Below the stripping device is a receiver 30, which is movable laterally by means of a lever mechanism 34, so that the receiver can be moved to a position under the cathode when the latter is in its raised position.

The arrangement is such that at least the cathode, the stripping device and the receiver are enclosed within a protective container 32 iilled with a protective gas, and in which a pressure above that of the atmosphere is maintained, in order to prevent the access of air.

As shown, there is provided above on the top of the cell a flap 64, consisting, for example, of graphite, which shuts off the cathode chamber from the protective chamber 32.

The operation of the apparatus is as follows: When suicient metal 36 has been deposited on the cathode 16, the latter being in the position shown in the drawing, the cathode is withdrawn from the bath by the operation of the lifting device 26 and pulled up into the cathode enclosure 22. During this operation the stripping edge 28 strips the deposited metal 36 from the cathode and the metal is collected, in the receiver 30, which has been previously moved to its position beneath the stripping edge.

Advantageously, the driving means for the lever mechanism 34 is coupled with the operation of the lifting device 26, so that the receiver 3) is automatically moved under the stripping device as the cathode is withdrawn.

The protective chamber 32 is externally cooled by means of a cooling coil 38. When the material has been stripped from the cathode, the receiver is returned to its initial position so that the clean cathode can be reintroduced into the melt, and the deposition process is continued. The stripped material remains in the receiver until it has cooled to a temperature at which it can be exposed to the atmosphere without the risk of gas absorption. When this temperature has been reached, the receiver 30 is emptied by means of a flap 42 pivotable about a hinge 40.

In the apparatus shown in the drawing there are provided two cathode enclosures 22 and 52 which are pivotably arranged in such manner that one of the enclosures is always positioned above the cell in alignment with the axis of the cathode. For this purpose, both enclosures 22 and 52 are mounted on a base plate 56 which is pivotable about an axis 54. The plate 56 is mounted on a corrugated tube 58 which enables the plate to move and the plate and corrugated tube are connected to a stationary part of the protective chamber 32 in a gas-tight manner. Both enclosures 22 and 52 have at their upper end a stuiiing box 25 and 55, respectively, which keeps the upper end 20 of the cathode central during its movement, and forms a gas-tight seal for the protective gas chamber. The use of two cathode enclosures enables the cathode not in operation to be exchanged while the other cathode is in operation. For this reason the releasable coupling 24 is provided between the lifting device 26 and the upper end 20 of the cathode. Since each cathode enclosure also acts as a cooling device for a retracted cathode, the non-operative cathode can be exchanged after a short cooling period. By using two pivotable cathode enclosures two cathodes may be operated alternatively. This expedient is very advantageous in electrolytic systems in which the melt causes corrosion of the cathode, so that it is necessary to remove and clean the cathode after each charge.

What is claimed is:

1. Apparatus for producing high melting metals by electrolysis of electrolytic charge comprising a cell for holdingrsaid electrolytic charge, a plurality of cathodes movable selectively into and out of said cell, means for moving said cathodes, said means comprising a lifting w device for selectively raising and lowering said cathodes, enclosure means surrounding said cathodes and insulating said cathodes from the atmosphere, said enclosure means being mounted on a support plate pivotally attached to said container whereby said cathodes are selectively positionable for insertion into said cell, said support plate being attached to said cell by a corrugated tube, said enclosure means, corrugated tube and container` means forming an envelope insulated from the atmosphere, means for stripping said cathodes of high melting metal depositable thereon, receiver means for collecting high melting metal stripped from said cathodes, said receiver means being movable with respect to said cathodes into and out of a position under said cathodes.

2. Cell of claim l wherein said receiver means is a horizontally movable container.

3. Cell of claim 2 wherein said lifting device is a hydraulic cylinder with a piston releasably attachable to said cathodes.

References Cited in the le of this patent UNITED STATES PATENTS 2,879,213 Howard Mar. 24, 1959 2,887,443 Blue et al May 19, 1959 2,943,032 Benner June 28, 1960 2,957,816 Sarla et al. Oct. 25, 1960 3,003,934 Slatin Oct. 10, 1961 

1. APPARATUS FOR PRODUCING HIGH MELTING METALS BY ELECTROLYSIS OF ELECTROLYTIC CHARGE COMPRISING A CELL FOR HOLDING SAID ELECTROLYTIC CHARGE, A PLURALITY OF CATHODES MOVABLE SELECTIVELY INTO AND OUT OF SAID CELL, MEANS FOR MOVING SAID CATHODES, SAID MEANS COMPRISING A LIFTING DEVICE FOR SELECTIVELY RAISING AND LOWERING SAID CATHODES, ENCLOSURE MEANS SURROUNDING SAID CATHODES AND INSULATING SAID CATHODES FROM THE ATMOSPHERE, SAID ENCLOSURE MEANS BEING MOUNTED ON A SUPPORT PLATE PIVOTALLY ATTACHED TO SAID CONTAINER WHEREBY SAID CATHODES ARE SELECTIVELY POSITIONABLE FOR INSERTION INTO SAID CELL, SAID SUPPORT PLATE BEING ATTACHED TO SAID CELL B A CORRUGATED TUBE, SAID ENCLOSURE MEANS, CORRUGATED TUBE AND CONTAINER MEANS FORMING AN ENVELOPE INSULATED FROM THE ATMOSPHRE, MEANS FOR STRIPPING SAID CATHODES OF HIGH MELTING METAL DEPOSITABLE THEREON, RECEIVER MEANS FOR COLLECTING HIGH MELTING METAL STRIPPED FROM SAID CATHODES, SAID RECEIVER MEANS BEING MOVABLE WITH RESPECT TO SAID CATHODES INTO AND OUT OF A POSITION UNDER SAID CATHODES. 